The invention relates to a method for producing an electrical thin layer circuit comprising at least one capacitor and one conductor path and/or a resistor, in which a layer of a tantalum-aluminum alloy with a tantalum proportion of between 30 and 70 atomic % is first applied onto an insulating substrate in order to form these circuit elements, and thereupon an additional layer of a tantalum-aluminum alloy with a tantalum share having a magnitude of between 2 and 20 atomic % is applied. An interruption is inserted into the two tantalum-aluminum layers with the aid of a first masking and etching technique at the location of a capacitor to be formed whereupon the tantalum-aluminum layers are anodically oxidized in order to produce a two-layer capacitor dielectric. A silicon-dioxide layer is applied onto the resulting tantalum-aluminum oxide layer, and finally an electrically properly conducting surface layer is produced on the capacitor dielectric. This can be done in the area of existing conductor paths with the aid of an additional masking and etching technique.
Up to now the production of integrated RC thin layer circuits in tantalum technique was only possible with the high technological expense of photolithographic processes. Depending upon the specific technological requirements, up to 12 photolithographic processes were required. The essential reason therefore is that the .beta.-tantalum provided in the tantalum technique as a base electrode for capacitors cannot selectively be etched from the tantalum-oxynitride developed for resistors on the basis of its high chemical stability. Therefore, locally delimited etching barriers are required, which necessarily increase the number of photolithographic processes required.
Utilizing the tantalum-aluminum double-layer technique known, for example, from U.S. Pat. No. 3,949,275, this problem does not exist since the aluminum-rich tantalum-aluminum layer provided as a base electrode for capacitors can readily be selectively etched from the tantalum-aluminum layer provided for resistors.
An additional improvement of the aforementioned tantalum-aluminum double-layer technique was obtained by the introduction of a two-layer capacitor dielectric known from German OS No. 2,506,065. This two-layer capacitor dielectric consists of a tantalum-aluminum oxide-layer produced by an anodic oxidation of the aluminum-rich tantalum-aluminum layer and a silicon-dioxide layer advantageously produced by cathode sputtering. For the RC thin layer circuits produced in accordance with this technology, the absolute values of the temperature coefficients of the resistors can be adjusted to the absolute values of the temperature coefficients of the capacitance. This adjustment results via the relationship ##EQU1## whereby .alpha.=temperature coefficient TKC of the two-layer dielectric,
.alpha..sub.1 =temperature coefficient TKC of the tantalum-aluminum oxide layer, PA1 .alpha..sub.2 =temperature coefficient TKC of the silicon dioxide layer, PA1 .epsilon..sub.1 =dielectric constant of the tantalum-aluminum oxide layer, PA1 .epsilon..sub.2 =dielectric constant of the silicon dioxide layer, PA1 d.sub.1 =thickness of the tantalum-aluminum oxide layer, and PA1 d.sub.2 =thickness of the silicon dioxide layer.
With the aid of this relationship, a suitable thickness d.sub.2 of the silicon dioxide layer can be adjusted relative to each arbitrary thickness d.sub.1 of the tantalum-aluminum oxide layer, so that the absolute value of the temperature coefficients of the capacitance corresponds with the absolute value of the temperature coefficient of a resistor.
The production of the thin layer circuits having a two-layer capacitor dielectric results in accordance with a method of the initially mentioned type, whereby the formation of the tantalum-aluminum oxide layer is applied with a local delimitation utilizing a dielectric puncture-resistant photomask. With a continued usage of this photomask and also using the lift-off technique, the desired two-layer dielectric consisting of tantalum-aluminum oxide and silicon oxide can be produced with the saving of an additional photomask. Thus, for the production of these thin layer circuits, four masks are required in all, whereby respectively a mask is required for the formation of the interruption, for the formation of resistors, and for the structuring of the surface layer in addition to the aforementioned mask.